This invention relates to inexpensive slippers and more particularly to disposable plastic slippers made from third web bubble plastic cushioning material.
It is well known to make slippers and other footwear out of plastic materials and even plastic coated paper when they are to be used briefly and then thrown away, such as at public baths, swimming pools, hotels and hospitals.
U.S. Pat. No. 4,112,599 issued Sep. 12, 1978 to Krippelz discloses slippers made from common two web bubble wrap sheet material commonly used in cushioning packages. This is made from two thin polyethylene plastic sheets. A first cushioning sheet is formed with a plurality of separate and independent 1/2 inch diameter pockets spaced apart about 1/16 inch. A second planar sheet is sealed against the concave side of the first sheet to close the pockets or bubbles and seal air in each bubble. The slippers are fashioned with the convex side of the bubbles against the foot so that there will be ample ventilation at the foot surface by the spaces between the bubbles enabling air and moisture to move freely against the skin while the bubbles cushion the step.
This avoids what he refers to as the "plastic raincoat effect" of perspiration and dampness when sheet plastic is in contact with the skin. However, there are unfortunate consequences of this type of construction. Because the heel produces extraordinary pressure forces on the bubbles when walking,, they are easily burst. Then one is walking on a thin sheet of plastic without cushioning. Sliding the foot into a slipper lined with bubbles is very difficult, because the bubbles create a high friction surface. His structure includes an outsole attached to the insole with the bubbles extending outward to the floor. This increases the frictional resistance of the slipper against the floor. With a loose fitting slipper of this sort, it is preferable to have an outsole with a low friction surface.
Good quality slippers have an upstanding heel portion that prevents the annoying tendency for the heel portion of the sole to fold under in use. Scuff-type slippers i.e. those without an upstanding heel portion are so inexpensive to fabricate that most disposable slippers, including the Krippelz slipper are of the scuff type. U.S. Pat. No. 4,145,822 issued Mar. 27,1979 to Mitchell incorporates special structure to overcome this tendency for the heel portion of the sole to fold under but at considerable cost and complexity.